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| author | Ian Lance Taylor <iant@golang.org> | 2021-05-25 16:31:41 -0700 |
|---|---|---|
| committer | Ian Lance Taylor <iant@golang.org> | 2021-06-01 19:59:18 +0000 |
| commit | 24e9707cbfa6b1ed6abdd4b11f9ddaf3aac5ad88 (patch) | |
| tree | 0b9fad4006bd549b9813255c6b540651f7bcb6a9 /src/cmd/cgo | |
| parent | 272552275f56345095b4ea7f404e5b317856cf07 (diff) | |
| download | go-24e9707cbfa6b1ed6abdd4b11f9ddaf3aac5ad88.tar.gz go-24e9707cbfa6b1ed6abdd4b11f9ddaf3aac5ad88.zip | |
cmd/link, cmd/cgo: support -flto in CFLAGS
The linker now accepts unrecognized object files in external linking mode.
These objects will simply be passed to the external linker.
This permits using -flto which can generate pure byte code objects,
whose symbol table the linker does not know how to read.
The cgo tool now passes -fno-lto when generating objects whose symbols
it needs to read. The cgo tool now emits matching types in different
objects, so that the lto linker does not report a mismatch.
This is based on https://golang.org/cl/293290 by Derek Parker.
For #43505
Fixes #43830
Fixes #46295
Change-Id: I6787de213417466784ddef5af8899e453b4ae1ad
Reviewed-on: https://go-review.googlesource.com/c/go/+/322614
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
Diffstat (limited to 'src/cmd/cgo')
| -rw-r--r-- | src/cmd/cgo/gcc.go | 2 | ||||
| -rw-r--r-- | src/cmd/cgo/out.go | 16 |
2 files changed, 15 insertions, 3 deletions
diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go index ae61725bc7..a73e998877 100644 --- a/src/cmd/cgo/gcc.go +++ b/src/cmd/cgo/gcc.go @@ -1638,6 +1638,8 @@ func (p *Package) gccCmd() []string { c = append(c, "-maix64") c = append(c, "-mcmodel=large") } + // disable LTO so we get an object whose symbols we can read + c = append(c, "-fno-lto") c = append(c, "-") //read input from standard input return c } diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go index 8c31d5b794..94152f4278 100644 --- a/src/cmd/cgo/out.go +++ b/src/cmd/cgo/out.go @@ -168,8 +168,18 @@ func (p *Package) writeDefs() { if *gccgo { fmt.Fprintf(fc, "extern byte *%s;\n", n.C) } else { - fmt.Fprintf(fm, "extern char %s[];\n", n.C) - fmt.Fprintf(fm, "void *_cgohack_%s = %s;\n\n", n.C, n.C) + // Force a reference to all symbols so that + // the external linker will add DT_NEEDED + // entries as needed on ELF systems. + // Treat function variables differently + // to avoid type confict errors from LTO + // (Link Time Optimization). + if n.Kind == "fpvar" { + fmt.Fprintf(fm, "extern void %s();\n", n.C) + } else { + fmt.Fprintf(fm, "extern char %s[];\n", n.C) + fmt.Fprintf(fm, "void *_cgohack_%s = %s;\n\n", n.C, n.C) + } fmt.Fprintf(fgo2, "//go:linkname __cgo_%s %s\n", n.C, n.C) fmt.Fprintf(fgo2, "//go:cgo_import_static %s\n", n.C) fmt.Fprintf(fgo2, "var __cgo_%s byte\n", n.C) @@ -1042,7 +1052,7 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) { // This unpacks the argument struct above and calls the Go function. fmt.Fprintf(fgo2, "func _cgoexp%s_%s(a *%s) {\n", cPrefix, exp.ExpName, gotype) - fmt.Fprintf(fm, "int _cgoexp%s_%s;\n", cPrefix, exp.ExpName) + fmt.Fprintf(fm, "void _cgoexp%s_%s(void* p){}\n", cPrefix, exp.ExpName) if gccResult != "void" { // Write results back to frame. |